In this paper

the advantages and disadvantages of different low voltage ride through methods for the direct drive wind turbine are studied. A kind of integrated strategy of low voltage ride through which is suitable for different voltage sag is proposed with combination of structure feature of the direct drive wind turbine

that is to reduce the output of generator

to combine unloading circuit of the variable resistance with control of the pitch angle and

on the principle of avoiding overvoltage of DC capacitor and over speed of generator

assure safe operation of the generator and converter. The reactive power support is provided by the side converter and

at the same time

reactive power compensation is made by the use of dynamic reactive power compensation device which is based on the magnetically controlled reactor（MCR in short）. The model of direct drive permanent magnet wind turbine generator based on integrated control strategy is constructed on the PSCAD platform. The low voltage ride through ability of the direct drive permanent magnet wind turbine generator at different voltage sag and feasibility of the integrated control strategy are verified by the simulation. It is shown by the study that the integrated strategy of low voltage ride through can improve the low voltage ride through ability of generator and stable operation ability of wind turbine generator after the fault ride through.